Eleven minutes: what a working day actually looks like

In 2005 three researchers followed twenty four office workers with stopwatches. The numbers they came back with explain more about your week than any productivity advice you have ever been given.

The UnaTask team, Building UnaTask. Aug 21, 2026. 6 min read.

You know the day. You were at your desk from nine, you did not slack off, you were busy the entire time, and at six you could not name one thing that moved. The usual explanation is that you need more discipline. There is a better one, and it was measured twenty years ago.

Twenty four people, followed with stopwatches

In 2005, Gloria Mark, Victor González and Justin Harris published a study at CHI with an unglamorous method: they followed twenty four information workers around their offices and recorded every switch they made. Not what people said about their day. What their day actually was.

They grouped work into what they called working spheres: threads of activity that belong together, the way a proposal and the emails about the proposal belong together. Then they timed them.

The number they report is 11 minutes and 4 seconds: the average time spent in a working sphere before switching to another one or being interrupted. The standard deviation they report alongside it is larger than the average itself, 18 minutes 9 seconds, which is a statistician's way of saying those stretches were wildly uneven. Some were seconds. A handful were long. Most were nowhere near long enough.

Eleven minutes is how long a piece of work lasted before something else took it away. Not on a bad day. On an average one.

Three more numbers, and then the shape appears

11.7 different threads of work touched in a single day, on average.
57 percent of them were interrupted before they were finished.
When interrupted work was picked back up on the same day, which happened for 77 percent of it, the worker had passed through an average of 2.3 other threads first.

Read those together and something clicks. It is not that people are scattered by temperament. It is that a working day, left to arrange itself, arrives pre chopped. Eleven minutes is not enough to get properly into anything that requires holding several things in your head at once. And more than half of those short stretches did not even get to end on their own terms.

The resumption figure is the quiet one, and the one people skip. You do not return to a task. You return to a task through two other tasks, each of which leaves a little of itself behind. Sophie Leroy named that residue in 2009 and showed it degrades your performance on whatever you turn to next, and that it does not fade after a moment of settling in. It persists.

A number you have seen everywhere, which we are leaving out

You have almost certainly read that it takes 23 minutes and 15 seconds to recover from an interruption. It is on every productivity blog, in slide decks, in books.

There is no study. The figure traces back to a 2006 magazine interview with one of the authors above, with no method attached to it, and it has been repeated ever since without anybody going back to check. The underlying research on fragmented work is solid and worth citing, which is why the real numbers are in this piece. That one is not, so we left it out, and we would rather say so than quietly borrow the credibility.

What this changes about a block

If eleven minutes is the ambient rhythm of an unmanaged day, then blocking time is not a productivity flourish or a personality type. It is a deliberate act of aggregation: taking twelve scattered fragments that would have gone to six different things and forcing them to land on one.

It also sets a floor, and this is the practical part. A block shorter than the ambient fragmentation is not a block. It is a fragment with a name on it. Thirty minutes feels responsible and buys you nothing structural, because your day was already handing you stretches that long for free. If a block is going to do work that the day would not have done anyway, it has to be meaningfully longer than eleven minutes, which in practice means fifty at the low end and ninety when the work is hard.

One more finding, offered carefully because it is one study of twenty four people in specific offices. Working stretches in the morning were measurably shorter than in the afternoon. That is the opposite of the folk wisdom that mornings are the protected hours. Do not build doctrine on it. Do check your own pattern for a week before you hand your best work to a slot you chose by reputation.

This is one chapter of Blocks No. 01, a 26 page guide to time blocking. Free PDF, no email, and every number in it traced to the paper it came from. Get the full guide